This invention relates to a laser perforating apparatus for perforating workpieces such as paper, plastic film, or metal plate by means of a laser beam.
A laser perforating apparatus as shown in FIG. 1 has been heretofore proposed, wherein a laser beam 2 powered from a laser oscillator 1 is periodically passed by a rotary shutter rotatable via a motor 3. The laser beam 2 is thus periodically prevented from passing and is thus reflected. The laser beam 6 thus relfected is absorbed by a damper 5. The laser beam 11 which has passed through the rotary shutter 4 is led by a mirror 7 or the like to a working position and is condensed by a lens 8 to a predetermined position on a workpiece 9, so that the workpiece 9 is formed with a hole 10, the dimensions of which are determined by the speed of the motor 3 and the configuration of the rotary shutter 4, and the speed at which the workpiece 9 is moved.
The conventional laser perforating apparatus is fabricated as aforementioned to thus require the motor 3 to be rotated at about 30,000 rpm when the workpiece 9 is moved at higher speeds, for example, 120 m/min., to form holes with a pitch of 1 mm. Apparently, it has been impossible to realize such a motor in practice. Such a motor has a limited mechanical life, if any, and both the motor 3 and the shutter 4 are subjected to a high revolution rate which causes noise such as air cutting sounds and vibration noise, thereby creating an adverse work environment.
During the period of the passage of the rotary shutter 4 through the laser beam 2, or the reflection of the laser beam on the rotary shutter, disadvantages are caused such that the passing laser beam 11 is converted to a less than circular form when edges 12 of the rotary shutter 4 interfere with the laser beam 2, and the accuracy of the hole 10 to be formed in the workpiece 9 is de-graded by diffraction by the edges 12 so that the laser beam impinges on undesired portions.